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How healthy lungs develop in children

News 2021-65 EN

On average, a human being consists of about 30 trillion body cells - and just as many bacteria. Without them, we would not be able to live. Not only in the intestine, on our skin, or in the stomach do microorganisms perform essential tasks. The lungs also have a microbiome, a community of bacteria, viruses, and fungi that is indispensable for the organ’s function. A team led by DZL researcher Professor Dr. Dr. Burkhard Tümmler, research group leader Molecular Pathology of Cystic Fibrosis at the Department of Pediatric Pneumology, Allergology and Neonatology at Hannover Medical School (MHH), has now studied the composition of the lung flora in infants and toddlers with and without cystic fibrosis (cystic fibrosis) and found out how a healthy lower respiratory microbiome develops. The study was published in the prestigious journal Biofilms and Microbiomes.

Microorganisms form a community of life

"Until recently, the human lower respiratory tract was considered sterile," explains Professor Tümmler. As a result, most studies had examined the microbiology of the lungs only in acute infections or chronic lung diseases. "In our work, we collected cough swabs from healthy children aged three weeks to six years for the first time, tested them for the microorganisms present, and compared them with those from cystic fibrosis sufferers of the same age," explains the research group leader. To do this, the scientists had to overcome various hurdles. One particular challenge was the quality of the samples. After all, bacteria, viruses, and fungi are everywhere in the air and water. "In order not to accidentally contaminate the samples with foreign organisms, we had to be extremely careful during collection and further processing," emphasizes Marie-Madlen Pust, a doctoral student in the research group and lead author of the study. Another difficulty was filtering out the DNA of the many different microorganism species from each swab and assigning it correctly. "The respective secretion samples contained only a few billionths of a gram of genetic material, and about 90 percent of this came from the children and only ten percent from the microorganism community," explains the junior scientist. For the analysis, MHH bioinformaticians developed a so-called metagenome pipeline, read out the entire genetic material of the microbiome with the help of a sequencing machine, and then reassigned the massive unordered DNA data set to the corresponding microorganisms using high-performance computing technology.

Healthy and sick children temporarily have the same lung microbiome

The scientists found that the lung biome of healthy and sick children hardly differed from each other during the first three years of life. "They had a very similar composition of different bacterial species that seem to interact with each other and form a kind of network," says the first author. Surprisingly, this also includes disease germs such as Staphylococcus aureus or the dreaded cystic fibrosis pathogen Pseudomonas aeruginosa, an environmental germ found everywhere - including in drinking water. In the first year of life, this network is somewhat more unstable in children with cystic fibrosis (CF), but there is hardly any difference in two- to three-year-olds. Only with increasing age does the microbiome change again in CF sufferers. The diversity of bacterial species decreases, the disease germs predominate and chronically settle in the lungs, and the sensitive network breaks down. In healthy children, on the other hand, the network remains stable, even though their lungs have a much higher bacterial load.

"It is clear from our study that the overall composition of the microbiome is crucial for healthy lungs," emphasizes study leader Tümmler. This cohort of healthy children can be used as a comparative value for other studies in the future. "Up to now, only the findings of children with different diseases could be compared," explains the scientist. The study also provides a strong indication for the treatment of cystic fibrosis: While the treatment of older CF patients is only possible to a limited extent, there is a window of opportunity in young children to influence the lung's biological processes favorably for further course of the disease.


Further information:

The study was conducted with the DZL at the Hannover site and the Central MHH Research Unit for Gene Sequencing GENOMICS. It was funded by the Collaborative Research Center SFB 900 ("Microbial Persistence and its Control").

Source: idw

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